Compositions for reducing metal etch rates using stripper solutions containing copper salts

ABSTRACT

Resist stripping agents, useful for fabricating circuits and/or forming electrodes on semiconductor devices for semiconductor integrated circuits with reduced metal etch rates, particularly copper etch rates, are provided with methods for their use. The preferred stripping agents contain low concentrations of a copper salt with or without an added amine to improve solubility of the salt. Further provided are integrated circuit devices and electronic interconnect structures prepared according to these methods.

REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.11/928,754, filed on Oct. 30, 2007, which claims the benefit of U.S.Provisional Application No. 60/953,804, filed Aug. 3, 2007, both ofwhich are hereby incorporated herein by reference.

FIELD OF THE INVENTION

The present disclosure relates to a resist stripping agent containing ametal salt for use in fabricating circuits or forming electrodes onsemiconductor devices for semiconductor integrated circuits or liquidcrystal displays, and further to a process of producing semiconductordevices using the resist stripping agent, the stripping agent providingreduced metal etching during stripping procedures, and further to aprocess of producing semiconductor devices using the resist strippingagent to produce semiconductor devices without the loss of substantialamounts of metal from metal components.

BACKGROUND

The technology of fabricating semiconductor integrated circuits hasadvanced with regard to the number of transistors, capacitors and otherelectronic devices which can be fabricated on a single integratedcircuit chip. This increasing level of integration has resulted in largepart from a reduction in the minimum feature sizes of the integratedcircuits and an increase in the number of layers which make up theintegrated circuit. Today's design features, generally referred to as“sub-micron” have dropped below 0.25 microns. The manufacture ofintegrated circuit components having this reduced size has placed newdemands on all aspects of their production including the removal ofresists with chemical stripper solutions.

Semiconductor devices for semiconductor integrated circuits or liquidcrystal displays are commonly produced by a process including the stepsof coating a substrate with a polymeric resist composition; patterningthe resist film by exposure to light and subsequent development; etchingexposed portions of the substrate using the patterned resist film as amask to form minute circuits; and removing the resist film from theinorganic substrate. Alternatively, after forming minute circuits, theresist film can be ashed and the remaining resist residues removed fromthe substrate. A superior stripper solution should quickly remove resistresidues and materials at moderate to low temperatures, have anacceptable effect on the all exposed components, have a substantialcapacity for the dissolved resist and/or post etch residue to forestallboth the precipitation of solids and the early disposal of the strippersolution. A superior stripper solution should also quickly remove resistresidues in a rework process without substrate damage. Finally, superiorstripper solutions should exhibit minimal toxicity.

A variety of stripper solutions have been developed which have performedsatisfactorily in the manufacture of the early semiconductor devices. Asubstantial number of the early stripper solutions have been stronglyalkaline solutions. The use of the alkaline stripper solutions tomanufacture microcircuits containing metals, particularly tungsten orcopper and its alloys with aluminum, can lead to metal loss. Variousforms of metal loss, such as for example corrosion whiskers, pitting andnotching of metal lines, have been observed during the use of thesealkaline strippers. In the case of tungsten and copper, corrosion canoccur in the heated dry organic stripping composition mixtures withdissolved oxygen providing the cathodic reaction. Although such metallosses were acceptable in the manufacture of the early semiconductordevices, devices having sub-micron components cannot tolerate such metallosses.

Efforts have been made to reduce the loss of metal during thefabrication of semiconductor devices by utilizing stripper solutionscontaining a variety of corrosion inhibitors. U.S. Pat. Nos. 6,276,372;6,221,818; and 6,187,730 teach the use of a variety of gallic compoundswhich function as corrosion inhibitors in stripper solutions. U.S. Pat.Nos. 6,156,661 and 5,981,454 teach the use of an organic acid as acorrosion inhibitor in stripper solutions. U.S. Pat. Nos. 6,140,287;6,000,411; and 6,110,881 teach the use of chelating agents as corrosioninhibitors in stripper solutions. U.S. Pat. Nos. 5,902,780; 5,672,577;and 5,482,566 teach the use of dihydroxybenzene chelating agents ascorrosion inhibitors in stripper solutions. U.S. Pat. No. 5,997,658teaches the use of benzotriazole as a corrosion inhibitor in strippersolutions. U.S. Pat. No. 5,928,430 teaches the use of a gallic acid as acorrosion inhibitor in stripper solutions. U.S. Pat. No. 5,419,779teaches the use of catechol, pyrogallol, anthranilic acid, gallic acid,and gallic ester as corrosion inhibitors in stripper solutions.

The corrosion inhibitors used thus far generally have a number ofdrawbacks which can include the following: (a) they are organiccompounds not easily removed with a water rinse; (b) substantialquantities of the inhibitors are required and can affect the solution'sstripping abilities; (c) inhibitors having chelating properties canadhere to metal and other component surfaces and interfere withperformance; and (d) a component's toxicity and lack of biodegradabilitycan make exposure to solutions undesirable and disposal of spentstripper solutions more difficult.

What is needed is a stripper solution containing a component which: (a)can, at very low levels, prevent the dissolution of metals and theiralloys, including copper and other metals used in the fabrication ofsemiconductor devices; (b) is compatible with the stripper solution anddoesn't interfere with its operation; (c) can be easily rinsed from asemiconductor device with water and/or a water soluble alcohol, leavingno residues; and (d) has low toxicity and does not negatively impact thebiodegradability of the spent stripper solution. This present disclosureaddresses and resolves these needs.

SUMMARY

A general object of the present invention is to provide a compositionfor removing a photoresist from a substrate containing a metalliccomponent such as copper. As used herein, the term resist refers to aphotoresist or resist material, a post etch residue, or a combinationthereof. The composition includes a stripper solution and a copper salt,the composition having a metal conservation factor (MCF) having a valueof >0 and ≦1, where MCF is defined as:

${MCF} = \frac{\left( {a - b} \right)}{a}$

where “a” is an etch rate determined with a stripper solution notcontaining the copper salt and “b” is an etch rate determined withsubstantially the same stripper solution containing the copper salt.Other metal salts such as for example, cobalt salts can also be added tostripper solutions to similarly reduce the copper etch rate. A singlemetal salt or a combination of metal salts can similarly be utilized toreduce the etch rate of copper or another metal.

Preferred copper salts are soluble in the stripper solution selected. Ifsolubility of the copper salt is negligible or marginal, solubility ofthe salt in the stripper solution can be enhanced by the addition of amonomeric or polymeric amine. Such amine solubilized copper saltssimilarly reduce copper etch levels. Copper salts having a +1 and +2valence can be utilized. Examples of copper salts having such valencesinclude CuCl and Cu(NO₃)₂. A level of copper salt ranging from about0.001 g of copper salt for each 100 g of solution to about 0.1 g ofcopper salt for each 100 g of solution is generally preferred. A levelof copper salt ranging from about 0.005 g of copper salt for 100 g ofsolution to about 0.075 g of copper salt for 100 g of solution is morepreferred. A level of about 0.025 g of copper salt for 100 g of solutionis most preferred.

Reduced etch rates, as evidenced by a Metal Conservation Factor (MCF)ranging from greater than 0 and less than or equal to 1 has beenobserved upon adding a copper salt to a variety of stripper solutions,including commercial stripper solutions. Preferred stripper solutionswhich benefit from the addition of a copper salt are those comprisingdimethyl sulfoxide, a quaternary ammonium hydroxide, an alkanolamine,with or without secondary solvent, such as for example a glycol ether.

More preferred compositions including stripper solutions in combinationwith a copper salt are those comprising dimethyl sulfoxide, a quaternaryammonium hydroxide (the base), an alkanolamine, with or withoutsecondary solvent, such as for example a glycol ether, and having adryness coefficient (DC) of at least about 1 and more preferably atleast about 1.8, where the dryness coefficient is defined by theequation:

${{D\; C} = \frac{{mass}\mspace{14mu} {of}\mspace{14mu} {{base}/{mass}}\mspace{14mu} {of}\mspace{14mu} {solution}\mspace{14mu} {tested}}{{mass}\mspace{14mu} {of}\mspace{14mu} {{water}/{mass}}\mspace{14mu} {of}\mspace{14mu} {solution}\mspace{14mu} {tested}}}$

Another object of the present disclosure is to provide a composition forremoving a photoresist from a substrate containing metallic copper, saidcomposition comprising a stripper solution, a copper salt, and an amine,said composition providing a lower etch rate than said stripper solutionnot containing a copper salt. Amines suitable for incorporation into thestripper solution can be monomeric amines and/or polymeric amines. Allstripper solutions having the copper salt/amine combination added whichhave been tested have shown reduced copper etch rates. The coppersalt/amine combination is particularly suitable when a copper saltcannot be provided having sufficient solubility in the strippersolution.

Another object of the present disclosure is to provide a method forremoving a photoresist from a substrate containing metallic copper. Themethod includes the steps of providing a substrate having a photoresistand metallic copper thereon, and contacting the substrate with acomposition including a stripper solution and a copper salt, thestripper/salt combination having an MCF value of more than 0 and lessthan or equal to 1 to effect removal of the resist. Contacting thesubstrate with a composition involves a composition including coppersalts of the type discussed above, included in amounts described above,with or without an added amine. Monomeric or polymeric amines can beutilized. Preferred stripper solutions used in the contacting stepinclude are those described above. Other commercial stripper solutionscan also be advantageously combined with a copper salt to providereduced metal etch rates as described below.

The step of contacting can involve immersion of a substrate in astripper solution or by spraying the stripper solution onto thesubstrate using a spray tool. Further steps following contacting caninvolve the additional steps of removing the substrate from contact withthe stripper solution and/or rinsing the substrate with an appropriatesolvent. During the contacting step, the stripper solution is preferablymaintained at a temperature of at least about 50° C. and more preferablyat a temperature ranging from about 50° C. to about 85° C.

Another object of the present disclosure is to provide an electronicinterconnect structure prepared in part by removing resist residues froma substrate having metal components according to the method describedabove to produce an interconnect structure with increased levels ofintact metal. FIG. 2 illustrates a typical electronic interconnectstructure having trenches 1 and 2 interconnected through via 3 withintwo dielectric layers 5 and 6 separated by a barrier layer 4. Trenches 1and 2 and via 3 are typically filled with a metal such as copper.

Another object of the present disclosure is to provide an integratedcircuit device obtainable in part by processing wafers containing metalcomponents to remove resist residues according to the method describedabove with reduced metal etching. FIG. 3 illustrates a typicalintegrated circuit device having a plurality of computer chipsillustrated by 1 interconnected through chip routers illustrated by 2.

A still further object of the present disclosure is to provide a methodfor preparing a stripper solution that provides reduced metal etch ratesby providing a container; providing components of a stripper solution;providing a copper or cobalt salt; and adding the components and themetal salt to the container to provide contents within the container.Providing components can include providing individual components, acomposition containing various components, or combinations thereof.Further, adding components of a stripper solution can involve addingindividual components, premixed components, and/or a preformed strippersolution containing provided components in substantially any order. Acontainer can include substantially any vessel capable of holding astripper solution and includes a typical container used for shipping ortransporting a liquid product, equipment used to contain strippersolutions for use processing substrates to remove photoresists and/oretch residues. As used herein a vessel includes equipment used to holdand/or transport a stripper solution during the processing of substratesand includes, but is not limited to, holding and transfer vesselsincluding any pipe system used to transport a stripper solution.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a graphic representation of the relationship betweenthe copper salt content of a stripper solution and the copper etch ratewhich occurs upon exposing that solution to a substrate having exposedcopper metal.

FIG. 2 illustrates an electronic interconnect structure.

FIG. 3 illustrates an electronic device containing a plurality ofelectronic interconnect structures.

DESCRIPTION

For the purposes of promoting an understanding of the presentdisclosure, references will now be made to the embodiments illustratedand specific language will be used to describe the same. It willnevertheless be understood that no limitation of the scope of what isclaimed is thereby intended, such alterations and further modificationsand such further applications of the principles thereof as illustratedtherein being contemplated as would normally occur to one skilled in theart to which the disclosure relates.

The compositions according to this present disclosure include a strippersolution containing a copper salt with or without an amine. Suchcompositions have a copper conservation factor of more than 0 and lessthan or equal to 1, illustrating a reduction in the etch rate ofmetallic copper from a copper containing substrate in contact with thecomposition. Preferred stripper solutions include those comprisingdimethyl sulfoxide, a quaternary ammonium hydroxide, an alkanolamine,with or without secondary solvent such as for example a glycol ether.Preferred alkanolamines have at least two carbon atoms, at least oneamino substituent and at least one hydroxyl substituent with the aminoand the hydroxyl substituents attached to different carbon atoms. Apreferred quaternary ammonium hydroxide is tetramethylammoniumhydroxide. FIG. 1, based on data from Example 1 illustrates the effectof differing concentrations of a copper salt on stripper solutionscontaining dimethyl sulfoxide, monoethanolamine, tetramethylammoniumhydroxide, 3-methyl-3methoxybutanol, and a small amount of water on theetch rate of metallic copper. The test was carried out on substratescontaining metallic copper obtained from two sources. For the preferredstripper solutions, the copper etch rate was lowest at about 0.025 g ofCu(NO₃)₂ for 100 g of the stripper solution. The copper conservationfactors for the different solutions containing differing amounts ofcopper salts ranged from 0.26 to 0.93.

Reductions in the metal etch rate can be achieved by reducing the watercontent of the preferred stripper solution and by adding a copper salt.A combination of a dry stripper solution and the addition of a coppersalt can provide an additive benefit as illustrated in Example 2.Stripper solutions C and D differed only in the amount of water. As canbe seen from Table II, lowering the water content as reflected in eachsolution's dryness coefficient, reduced the copper etch rate. Theaddition of 0.025 weight % of Cu(NO₃)₂ either maintained a very lowcopper etch rate or further reduced the copper etch rate to provide afavorable metal conservation factor (MCF).

In Example 3, the copper etch rates and metal conservation factor (MCF)were determined with a variety of the preferred stripper solutions andwith stripper solutions based on other commercially available strippersolutions with and without the addition of 0.025 wt % of Cu(NO₃)₂. Forcompositions based on formulas 5, 6, and 7, the copper salt wasinsoluble and its effect could not be determined. All stripper solutionscapable of dissolving the copper salts exhibited reduced copper etchrates and displayed MCF values ranging between 0.18 and 1.00.

In Example 4, a method is provided for overcoming problems of thesolubility of the copper salt in stripper solutions unable to dissolve asufficient amount of the salt. The copper salt was added to the strippersolution designated as formula 7 along with either a monomeric orpolymeric amine to provide a homogeneous solution. Copper etch rateswere determined using the method described in Example 1 for the strippersolutions containing a copper salt and an amine. The results areprovided in Table IV. Each of the amine/copper salt combinations reducedthe copper etch rate and provided copper conservation factors of from0.11 to 0.99. Ethanolamine and linear poly-4-vinylpyridine were the mosteffective amines combined with Cu(NO₃)₂.

In Example 5, the copper etch rates for a stripper solution with andwithout the addition of a Cu(I) salt was determined using the techniquesdescribed above. Without the addition of the Cu(I) salt the copper etchrate was 3.5 Å/min. and with the addition of 0.025 wt. % of CuCl, thecopper etch rate dropped to 0.84 Å/min. and provided an MCF value of0.76.

In Example 6, the effect of a cobalt salt on the copper etch rate wasstudied on two stripper solutions. For the first solution, the copperetch rate with 0.025 wt. % of Co(NO₃)₂ dropped from 3.5 Å/min. to 0.87Å/min. providing an MCF of 0.75. For the second solution the copper etchrate with 0.025 wt. % of Co(NO₃)₂ dropped from 4.0 Å/min. to 1.69 Å/min.providing an MCF value of 0.58.

In Example 7, substrates containing a TiW alloy were subjected to avariety of stripper solutions with and without an added copper salt(copper nitrate). As in the previous examples the metal etch rates weredetermined for each stripper solution with and without added coppernitrate. Except for formula 7, which caused no etching with or withoutan added copper salt, all stripper solutions containing an added coppersalt provided reduced metal etch rates as evidenced by an MCF value ofgreater than zero.

Studies carried out thus far have indicated that metal salts such as forexample Cu (I) and (II), cobalt and the like, provide substantiallyreduced metal etch rates for semiconductor substrates containing avariety of metals. The reduction in metal etching of metals such ascopper and alloys such as TiW subjected to a stripping solution toremove resist materials is particularly advantageous. For metalsalt/stripper solution combinations in which the metal salt is notsufficiently soluble, the addition of an amine has provided solubilityfor the salt and the metal/amine salt combination has provided reducedmetal etch rates. The metal salts, with or without amines, arecompatible with a range of stripper solutions, do not interfere with thestripper solution's operation, can be easily rinsed from a semiconductordevice or component with water or an alcohol, leaving no residues thatcould interfere with the device's operation, and finally, the metalsalts utilized at very low concentrations do not negatively interferewith the biodegradability of the spent stripper solutions.

While applicant's disclosure has been provided with reference tospecific embodiments above, it will be understood that modifications andalterations in the embodiments disclosed may be made by those practicedin the art without departing from the spirit and scope of the invention.All such modifications and alterations are intended to be covered.

EXAMPLES Example 1 Etch Rates as a Function of Copper Concentration

Stripper solutions A and B were prepared for etch rate studies havingthe following formulations: Solution A—81.9% dimethyl sulfoxide, 3.0%monoethanolamine, 2.55% tetramethylammonium hydroxide, 10%3-methyl-3-methoxybutanol, and 2.55% water and Solution B—81.5% dimethylsulfoxide, 4.5% monoethanolamine, 2.0% tetramethylammonium hydroxide,10% 3-methyl-3-methoxybutanol, and 2.0% water. A 33% aqueous solution ofCu(NO₃)₂ was prepared. Portions of stripper solutions A and B werecombined with sufficient copper solution to provide concentrations ofcopper in the stripper solution of 0.005%, 0.01%, 0.025%, 0.05%, and0.075%. Control solutions were used in the following etch rate studieshaving no copper salt added.

Commercial sources of silicon wafers with blanket plasma vapor depositedthin copper films were divided into approximately 2 cm by 2 cm testsamples for the study. The copper film thickness of each piece wasmeasured three times using a four point probe and the average filmthickness taken as the initial copper film thickness. For each solutiontested, three test samples were immersed in a stripper solution for 60minutes, rinsed and the copper film thickness measured again for eachtest sample. An average of copper film thickness for each test samplewas taken as the resultant copper film thickness. A loss of copper filmthickness was determined by subtracting the resultant copper filmthickness from the initial film thickness. The loss of copper filmthickness (in angstroms) observed in 60 minutes was divided by 60 togive an etch rate in the units of angstroms/minute. Table I belowsummarizes the etch rates determined for stripper solutions A and Bcontaining different levels of copper salt. FIG. 1 illustrates theseresults graphically. The copper salt could be added directly to strippersolutions A and B, but dissolution was slow and didn't appear to offerany advantage over adding the salt as an aqueous solution, provided thelevels of water were minimized. Similarly, the copper salt could also bedissolved in a compatible component of a stripper solution prior toadding the remaining components.

TABLE I Etch Rate for Percent Solution A Etch Rate for Solution BCu(NO₃)₂ Angstroms/minute MCF Angstroms/minute MCF 0.075 1.9 0.55 1.40.53 0.050 0.3 0.93 1.7 0.43 0.025 0.3 0.93 0.2 0.93 0.010 1.2 0.71 1.40.53 0.005 3.1 0.26 1.6 0.47 Control 4.2 3.0 (0.000)

Example 2 Copper Etch Rates for Different Sources of Copper Wafers inStripper Formulations having Different Dryness Coefficients, with andwithout the Addition of a Copper Salt

Two stripper solutions were prepared having the following components:Solution C—85.5 g of dimethyl sulfoxide, 6.0 g of diethylene glycolmonomethyl ether, 2.7 g of aminoethylethanolamine, 2.75 g oftetramethylammonium hydroxide, and 2.75 g of water; Solution D—85.5 g ofdimethyl sulfoxide, 6.0 g of diethylene glycol monomethyl ether, 2.7 gof aminoethylethanolamine, 2.75 g of tetramethylammonium hydroxide, and0.45 g of water. Solution C had a dryness coefficient of 1 and solutionD had a dryness coefficient of 11.9. Utilizing the test method describedin Example 1, etch rates were determined for each of these solutionswith the addition of 0.025% of a copper salt and without addition of thesalt (control). Parallel tests were conducted on test samples derivedfrom wafers having copper films applied by physical vapor depositionobtained from two different sources. Table II provides a summary of theetch rates obtained. Although there was some slight variation betweenwafers obtained from different source, reduced etch rates were observedwith solutions having a higher dryness coefficient and with solutionscontaining 0.025% copper nitrate, regardless of the source of thewafers.

TABLE II Dryness (a)* Cu Etch Rate (b)* Cu Etch Rate Stripper SolutionCoefficient (angstroms/minute) MCF (angstroms/minute) MCF C (control -no 1 2.6 2.7 Cu(NO₃)₂) C 1 0.0 1.00 0.3 0.96 (with 0.025% Cu(NO₃)₂) D(control - no 11.9 0.97 2.5 Cu(NO₃)₂) D 11.9 0.13 0.87 0.0 1.00 (with0.025% Cu(NO₃)₂) *The (a) and (b) etch rates were determined on testsamples obtained from two different suppliers.

Example 3 Copper Etch Rates for Copper Wafers in a Variety of StripperSolution Formulations with and without the Addition of a Copper Salt

A variety of stripper solution formulations provided in Table III belowwere contacted with test strips of the type described in Example I asdescribed therein. Each formulation was tested with and without addedcopper salt and the copper etch rates determined. Formulationscontaining an added copper salt contained 0.025% Cu(NO₃)₂. As noted inTable III, the copper salt was not soluble in some formulations.

TABLE III Copper Etch Rate (Å/min.) Dryness without Cu Formula #Formulation Coefficient pH salt with Cu salt MCF 1 81.5% DMSO 1 11.38 40.3 0.93  4.5% monoethanolamine  2.0% tetramethylammonium hydroxide  10% 3-methyl-3-methoxybutanol  2.0% water 2 81.9% DMSO 1.2 11.49 3.50.2 0.94  3.0% monoethanolamine 2.55% tetramethylammonium hydroxide  10% 3-methyl-3-methoxybutanol 2.55% water 3   86% DMSO 1 11.34 2.6 01.00   6% diethylene glycol monomethyl ether  2.7% tetramethylammoniumhydroxide  2.5% aminoethylethanolamine  2.8% water 0.03% surfactant* 4  88% DMSO 11.9 11.34 1 0.13 0.87   6% diethylene glycol monomethylether  2.7% tetramethylammonium hydroxide  2.8% aminoethylethanolamine 0.5% water 0.03% surfactant* 5   65% DMSO 1 11.80 1.2 Cu salt not —  25% monoethanolamine soluble   5% tetramethylammonium hydroxide   5%water 6   45% DMSO 1 12.03 3.3 Cu salt not —   25% monoethanolaminesoluble   10% tetramethylammonium hydroxide   10%3-methyl-3-methoxybutanol   10% water 7   92% DMSO 0.3 11.38 43 Cu saltnot —   2% tetramethylammonium hydroxide soluble   6% water 8   80% DMSODryness 11.87 47.2 38.8 0.18   10% N-methylpyrrolidone coefficient  5.5%methanol not  4.5% choline applicable 9 29.5% 2-aminoethoxyethanolDryness 10.82 4 0.5 0.85   30% N-methylpyrrolidone coefficient   5%γ-butryolactone not  0.5% resorcinol applicable *Zonyl ® FSO fluorinatedsurfactant available from E. I. DuPont de Nemours and Company, 1007Market St, Wilmington Delaware 19898 and “Zonyl” is a registeredtrademark of that same company.For some of the stripper solutions, a dryness coefficient was notapplicable because the stripper solution contained no quaternaryammonium hydroxide.

Example 4 The Enhancement of Copper Salt Solubility by a Monomeric orPolymeric Amine and Resultant Reduction in Copper Etch Rates

As can be seen from Example 3, copper nitrate was not soluble in severalof the stripper formulations tested. Solubility of the copper salt inthe stripper formulations can be enhanced by the incorporation of amonomeric or polymeric amine along with the copper salt. Severalamine/copper salt combinations were investigated with regard tosolubility in formula 7 of Example 3 and with regard to the effect ofthe combinations on the copper etch rate. The etch studies were carriedout as described in Example 1. Two approaches were utilized toincorporate the amine/copper salt combination into the strippersolution. The first approach involved preparing a 33.3 wt. % aqueoussolution of Cu(NO₃)₂ and adding the appropriate amount of solution to astripper solution containing the amine with agitation. A second approachinvolved preparing a 50 wt. % aqueous solution of Cu(NO₃)₂, adding theappropriate amount of this solution to the appropriate amount of amineand adding the aqueous amine/nitrate solution to the stripper solutionwith agitation. Other possible methods of addition can be envisioned byone skilled in the art and as a result this disclosure is not intendedto be limited by the particular methods provided herein.

As can be seen from the results provided in Table IV, the addition of amonomeric or polymeric amine can enhance the solubility of a copper saltin a stripper solution and reduce the copper etch rate observed for thestripper solution containing the amine/copper salt. In the examples, theamount of DMSO in the formula was reduced by the amount of amine added.

TABLE IV Solubility Copper of Etch Rate Formulation Cu(NO₃)₂ (Å/min.)MCF 92 g DMSO Not 43 NA 2 g tetramethylammonium hydroxide Applicable 6 gwater 92 g DMSO Insoluble No NA 2 g tetramethylammonium hydroxideResults 6 g water 0.025 g Cu(NO₃)₂ 82 g, DMSO Soluble 0.58 0.99 2 gtetramethylammonium hydroxide 6 g of water 8 g ethanolamine 0.025 gCu(NO₃)₂ 91.5 g, DMSO Soluble 0.85 0.98 2 g tetramethylammoniumhydroxide 6 g of water 0.5 g linear poly-4-vinylpyridine* 0.025 gCu(NO₃)₂ 91.5 g, DMSO Soluble 32.3 0.25 2 g tetramethylammoniumhydroxide 6 g of water 0.5 g piperidine 0.025 g Cu(NO₃)₂ 91.5 g, DMSOSoluble 38.1 0.11 2 g tetramethylammonium hydroxide 6 g of water 0.5 gmorpholine 0.025 g Cu(NO₃)₂ *REILLINE ™ 400 available from Vertellus,Inc. (formerly, Reilly Industries, Inc.), Indianapolis, IN

Example 5 Reduced Etch Rates with a Cu(I) Salt

A stripper solution was utilized in this example comprising 81.9%dimethyl sulfoxide, 3.0% monoethanolamine, 2.55% tetramethylammoniumhydroxide, 10.0% 3-methyl-3-methoxybutanol, and 2.55% water. The drynesscoefficient for the formulation was 1.2. The copper etch rate for thisformulation was determined as described above and found to be 3.5 λ/min.CuCl (0.025 parts) was dissolved in 100 parts of a stripper solution andthe copper etch rate determined in the manner described. The copper etchrate determined for the solution containing CuCl was 0.84 Å/min and theMCF was determined to be 0.76.

Example 6 The Reduction of Etch Rates with of Cobalt Salt

The stripper solution from Example 5 containing 81.9% dimethylsulfoxide, 3.0% monoethanolamine, 2.55% tetramethylammonium hydroxide,10.0% 3-methyl-3-methoxybutanol, and 2.55% water was used in thisexample to study copper etch rates in the stripper solution with andwithout the addition of a cobalt salt. Without any added salt thestripper solution had a dryness coefficient of 1.2 and provided a copperetch rate was 3.5 Å/min determined according to the method describedabove. Co(NO₃)₂ (0.025 parts) was added to this stripper solution as a25 wt % aqueous solution to a stripper solution (100 parts) and thecopper etch rate again determined as 0.87 Å/min. The stripper solutioncontaining the cobalt salt had an MCF of 0.75.

The copper etch rate for a second stripper solution comprising 81.5%dimethyl sulfoxide, 4.5% monoethanolamine, 2.0% tetramethylammoniumhydroxide, 10.0% 3-methyl-3-methoxybutanol, and 2.0% water and a drynesscoefficient of 1.0 was determined to be 4.0 Å/min. Co(NO₃)₂ (0.025parts) was added to this stripper solution as a 25 wt % aqueous solutionto a stripper solution (100 parts) and the copper etch rate againdetermined as 1.69 Å/min. The second stripper solution containing acobalt salt had an MCF of 0.58.

Example 7 Titanium Tungsten (TiW) Etch Rates for TiW Wafers in a Varietyof Stripper Solution Formulations with and without the Addition of aCopper Salt

A variety of stripper solutions formulations provided in Table V belowwere contacted with test strips. The test strips were cleaved fromcommercial sources of silicon wafers with blanket plasma vapor depositedthin TiW films and were approximately 2 cm by 2 cm in size. The TiW filmthickness of each piece was measured three times using a four pointprobe and the average film thickness was calculated as the initial TiWfilm thickness. For each solution tested, three test samples wereimmersed in a stripper solution for 30 minutes, rinsed and the TiW filmthickness measured again for each test sample. An average of TiW filmthickness for each test sample was taken as the resultant TiW filmthickness. A loss of TiW film thickness was determined by subtractingthe resultant TiW film thickness from the initial film thickness. Theloss of TiW film thickness (in angstroms) observed in 30 minutes wasdivided by 30 to give an etch rate in the units of angstroms/minute.Each formulation was tested with and without added copper salt and theTiW etch rates determined. The formulations containing an added coppersalt contained 0.025% Cu(NO₃)₂.

TABLE V TiW Etch Rate (Å/min.) Dryness without Cu Formula # FormulationCoefficient pH salt with Cu salt MCF 1 81.5% DMSO 1 11.38 5.2 1.6 0.69 4.5% monoethanolamine  2.0% tetramethylammonium hydroxide   10%3-methyl-3-methoxybutanol  2.0% water 2 81.9% DMSO 1 11.49 6.0 0.4 0.93 3.0% monoethanolamine 2.55% tetramethylammonium hydroxide   10%3-methyl-3-methoxybutanol 2.55% water 3 29.5% 2-aminoethoxyethanolDryness 10.82 0.2 0.1 0.50   30% N-methylpyrrolidone coefficient   35%ethylene glycol butyl ether not   5% γ-butryolactone applicable  0.5%resorcinol 4   65% DMSO 1 11.80 1.3 0.6 0.54   25% monoethanolamine   5%tetramethylammonium hydroxide   5% water 5   45% DMSO 1 12.03 4.1 1.20.71   25% monoethanolamine   10% tetramethylammonium hydroxide   10%3-methyl-3-methoxybutanol   10% water 6   86% DMSO 1 11.34 .4 0.7 0.75  6% diethylene glycol monomethyl ether  2.7% tetramethylammoniumhydroxide  2.5% aminoethylethanolamine  2.8% water 0.03% surfactant* 7  88% DMSO  11.9 11.34 0 0 0   6% diethylene glycol monomethyl ether 2.7% tetramethylammonium hydroxide  2.8% aminoethylethanolamine  0.5%water 0.03% surfactant* *Zonyl ® FSO fluorinated surfactant availablefrom E. I. DuPont de Nemours and Company, 1007 Market St, WilmingtonDelaware 19898 and “Zonyl” is a registered trademark of that samecompany.

While applicant's invention has been described in detail above withreference to specific embodiments, it will be understood thatmodifications and alterations in embodiments disclosed may be made bythose practiced in the art without departing from the spirit and scopeof the invention. All such modifications and alterations are intended tobe covered. In addition, all publications cited herein are indicative ofthe level of skill in the art and are hereby incorporated by referencein their entirety as if each had been individually incorporated byreference and fully set forth.

1. A composition for removing a resist from a metal-containing substrate, comprising a photoresist stripper solution and a copper metal salt.
 2. The composition of claim 1 wherein said photoresist stripper solution comprises dimethyl sulfoxide (DMSO), a quaternary ammonium hydroxide, and an alkanolamine.
 3. The composition of claim 1 wherein said composition comprises from about 0.001 wt. % to about 0.10 wt. % copper salt.
 4. The composition of claim 3 wherein said composition comprises from about 0.005 wt. % to about 0.075 wt. % copper salt.
 5. The composition of claim 4 wherein said composition comprises about 0.025 wt. % copper salt.
 6. The composition of claim 1 wherein said composition includes a monomeric or polymeric amine effective for improving the solubility of the copper salt in the solution.
 7. The composition of claim 1 wherein said composition further includes a secondary solvent.
 8. The composition of claim 7 wherein said secondary solvent is a glycol ether.
 9. The composition of claim 8 wherein said glycol ether is 3-methyl-3-methoxybutanol.
 10. The composition of claim 1 wherein said copper salt is CuCl or Cu(NO₃)₂.
 11. The composition of claim 1 wherein said alkanolamine has a least two carbon atoms, at least one amino substituent, and at least one hydroxyl substituent, with the amino and the hydroxyl substituents being attached to different carbon atoms.
 12. The composition of claim 1 wherein said alkanolamine is tetramethylammonium hydroxide.
 13. The composition of claim 2 wherein said alkanolamine is monoethanolamine. 